How do they purify Scrap Steel?

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sintro

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Mar 5, 2012
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I've been wondering for a while now, how do the refiners purify the scrap steel into one homologous type steel? They might get pots and pans, a car door, and some knife steel in there. So how do they purify the steel to fit a certain application, like knife steel? Or is scrap steel possibly not used for that?

If you had a bunch of s30v steel and wanted to refine it to be 1080 steel, is it possible?
 
Scrap is melted in an elctrode arc furnace. Impurities will typically float to the top and are "slagged off" as the furnace tips. Large bags of additives (vanadium, graphite, etc) are added to the melt to get the desired alloy. Furnaces I have worked on typically make rebar, or 1080, but the process is still pretty similar.
 
Onies gave a great answer. :thumbup:

There is an episode of one of those "how do they do it" shows where they show the process of making SS. It's pretty fascinating. I'm not sure which foundry they shot at, but the crucible was enormous! For some reason it made me feel nervous, which is odd I know. The electrodes that go into the crucible were huge, and for some reason they just seemed kind of scary. The operator sat in a glass rig way up over the whole thing and controlled it all, except when a worker in one of those heat resistant foil looking suits would come up and take a sample with a loooong ladle. They analyze the sample then add more scrap or whatever to get what they need.

Pretty cool really. :)
 
"kind of scary " ? Not at all .The electric furnaces I worked with 40 years ago were huge. Three 12" graphite electrodes were lowered into the scrap in the bottom. Then the fun began !! The electrodes caused huge arcs accompanied by lightning, thunder,flames , smoke - the fires of Hell ??
 
I work at a steel mill that makes rebar. We make lower grades of steel than knifemaker use for knives, but as far as purifying the liquid steel we used lime to help with sulfur. We also make low carbon wire grades that have to be pretty clean. We use lime, alsimin and calcium carbide. As far as taking s30v and making 1080, that depends on residules in the scrap. The EAF ( electric arc furnace) can't burn off certain alloys such as chrome, nickel, tin and moly. I'm not familiar with the chemistry of s30v so I don't know if it has higher chemistry than 1080.
 
mete said:
"kind of scary " ? Not at all .The electric furnaces I worked with 40 years ago were huge. Three 12" graphite electrodes were lowered into the scrap in the bottom. Then the fun began !! The electrodes caused huge arcs accompanied by lightning, thunder,flames , smoke - the fires of Hell ??
Click to expand...

Fires of hell, yup that sounds right!

These electrodes looked like they were at least 12' tall. Maybe much bigger. Scary on an elemental, primal level.

I imagine the first time they tested a nuke they felt the same way, only much stronger. Some people thought that it would fry all of the o2 and destroy the entire world. I can't even imagine what that must have been like!
 
I'm at work right now, sitting in my lab about 50' away from the furnace. Believe me, It's pretty scary. I used to work
On the floor, and after they would tap out (pour the liquid steel into a 90 ton ladle) I would have to get on a platform over the furnace and check for holes. That was really scary!
 
I heard that people put on two levels of hearing protection with an EAF. Also, what I was really trying to get at was this. If you took some s30v, which has vanadium in it, would you be able to purify it to something like 1080, which has no vanadium?

And Tlov, what elements of steel does the arc furnace usually leave behind after it's done heating up the steel?
 
Wet charges are the best, it'll put your heart straight in your throat and I don't even work on the EAF. I spend my time on the Caster. Scrap is brought into the yard and we segregate ours, not sure what determines the class of scrap, but you will busthlings, bundles. We make a bunch of different QBC grades from rebar to 7190's. Copper is probably our worst enemy. It is a really interesting process making steel, more like baking a cake..........a really hot one!

The noise at the EAF is unreal, and the light show!
 
We make low carbon steel ( .46 or so on finished rebar). As the EAF melts the scrap, the carbon and maganese will drop. The residules such as copper, nickel, chrome and moly will stay the same as the scrap mix before it was melted.
 
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